The Design of the flashing
A roll top ridge is the most common form of ridge capping used today. The profile is typically a rollformed section which means the
dimensions are standardised.
It is possible to produce a customised ridge capping, this is achieved by utilising tools that were used prior to the introduction of rollformers. If you are
considering using a customised ridge capping you will need to consider that it will be restricted to short lengths and the cost would be
considerably higher than a rollformed section.
Each suppliers ridge capping will be slightly different from the other manufacturers. It may also be possible for the profile to vary from
a supplier on a state to state basis depending on the rollformer that was used to manufacturer the product. Therefore it is impossible to say there are
standard dimensions for roll top ridge capping.
What is meant when someone refers to a 350 roll top ridge?
A typical ridge capping application
The measurement 350 refers to the cut size of the steel that the profile is rollformed from. If you were to squash the ridge back to a flat
piece of steel the width of the material would be 350mm. Some manufacturers produce additional sizes e.g. 405 roll top ridges. The additional
material is used to extend measurement 'D'; this can be useful for providing greater protection from wind driven rain or when capping low
pitch roofs. Instances may also arise where the top purlins are further apart and a standard ridge capping does not allow provide sufficient
coverage. The Australian Standards call for a minimum overlap of 100mm of the roof sheeting.
Additional ribs are added to the profile to add strength and reduce any possible oil canning of the steel.
Measurements for the CAD detail available for download:
Width of the roll 'A' is 57mm.
The effective cover 'B' of the ridge is 260mm an the pitch 'C' is 30 degrees.
Measure 'D' is 95mm.
Break to suit the profile: 28mm @ 150 degrees.
Scribing is the process of scalloping the break that match the roofing profile. Whilst this is not compulsory, it does give greater protection
from water blowing back under the flashing and aesthetically adds to the detail.
Customising Roll Top Ridge
Whilst a rollformed roll top ridge is a standard size there are slight adjustments that can aid in the installation process. These adjustments are typically done on a folding machine.
An example of this would be on a step pitch roof such as Tudor style. For this style roof the angle of a standard ridge 'C' would not be sufficient. Fasteners would pull the ridge in but in-between the fasteners the ridge would bludge outwards.
To solve the problem, the angle of 'C' could be increased by refolding the break, eliminating this problem (request this at the time of